Apparatus for measuring errors of refraction in the human eye.



No. 679,890. Patented Aug. 6, I90l.

L. L. FERGUSON. APPARATUS FUR MEASURING ERRORS 0F BEFRACTION IN THE HUMAN EYE.

. (Application filed July 18, 1900.

(No Model.)

*illli' Jlleilllli INVENTOR ATTORNEY 5 UNITED 3 STATES PATENT OFFICE.

LOUIS L. FERGUSON, OF NEW YORK, N. Y.

APPARATUS FOR MEASURING ERRORS OF REFRACTION IN THE HUMAN EYE.

SPECIFICATION forming part of Letters Patent N 0. 679,890, dated August 6, 1901.

Application filed July 18, 1900- Serial No. 24,066. (No model.)

To ctZZ whom it Wuty concern.-

Be it known that I, LOUIS L. FERGUSON, a citizen of the United States, and a resident of the borough of Manhattan, city and State of New York, have invented a new and useful Apparatus for Measuring Errors of Refraction in the Human Eye, of which the following is a specification.

This instrument, which I term a luxometer, is devised for the dual purpose of measuring the refraction in the human eye subjectively and objectively.

First, subjectively, by placing the patient in position to viewa distant test-card through a lens shiftable backward and forward in a guide having a scale marked to indicate the proper notation of the lens by its relative po sition between the eye and the test-card, resulting in the plus or minus rays which are necessary to correct hypermetropia and my opia, respectively. In the same connection I employ an auxiliary cylindrical test-lens for discovering astigmatism and indicating the nature and extent of the same. i

, tients eye through the medium of a stationary retinoscopic mirror, in combination with a shiftable light which is deflected upwardly,

v deflection of the retinoscopic mirror itself.

" beam D, in which slides a bar D.

end of the beam Dis mounted an eyepiece or In the accompanying drawings, Figure 1 is a perspective view of the apparatus. Fig. 2 is a front view thereof, on a larger scale, omitting the pedestal or support. Fig. 3 is a side elevation thereof, partly in section. Fig. 4 is a detail transverse section on the line 4 4, Fig. 1, showing the mode of mounting the retinoscopic mirror and the reflecting-mirror used in connection therewith, so that they may be. readily turned down out of the way when the instrument is to be used subjectively by means of test-cards, &c.

On a heavy base A and an extensible standardB B of common construction is a head 0, forming a support for a horizontally-slotted On one plate a of annular form to provide a sightaperture and provided with the customary cell a with springs-for the easy reception and removal of trial-lenses or with a guide a for the reception of a slide carrying trial-lenses of different powers, or the said plate a may be provided with both the cell a and the guide way a for a slide, as illustrated in the drawiugs. adjacent to the cell or lens-receiver a, is mounted a cell b for the reception of convex or concave lenses 1) for testing hypermetropia or myopia, respectively, and also for the reception of a cylindrical lens 11 for testing for astigmatism and capable of rotation in the customary manner The bar D is slid in either direction by rack and pinion c by means of a milled head 0' for the purpose of shifting the lens-cell b toa greater or less distance from the eyepiece a, and thus varying the relative distance of the'lens-cell b between the eye of the patient and a distant On the extremity of the sliding bar D', i

test-card for subjective examination or test. e represents a disk mounted by an arm on a pivot e and capable of oscillation to alimited extent, so as to throw the said disk to either side of the eyepiece oand on a level therewith in order to mask or occultthe eye of the patient which is not being examined. On the opposite or rear end of the beam D is mounted a perforated retinoscopic mirror fand back of this 'a plain mirror m, from which the ray of light from the eye of the patient in objective examinations is reflected through an inclined perforated disk n, mounted by a standard upon the beam D at proper height, distance, and angle, so that the operator looking from the point 0 may readily find and observe the said light-ray from the eye of the patient. The retinoscopic mirror f and the reflector m are pivoted for adjustment in a longitudinal vertical plane, so that they may be set at the proper angle of ad.- j ustment, and they are securely held in this fixed position of adjustment while in use.

In order to dispense with the necessity of shifting the retinoscopic mirror f to various angles with relation to the fixed light, asis usual in retinoscopic examinations, I provide a movable incandescent electric lamp h on the extremity of a rod g, mounted by a universal joint Z upon a standard Z on the fixed too . rection upon the universal joint Z as a center.

i represents the customary positive and negative conducting-Wires of the lamp h, by

which a current of electricity may be con veyed from a dry-cell battery or other source I tatable toany angle in the normal plane, permits the rod and the light to be moved unof electricity.

The rod 9 near the end on which the handle g is mounted passes through a diametric slot is in adisk is, which is rotatably mounted within a cellj, on which is marked a protractor-scalej, as to indicate accurately the inclination assumed by the slot is in the disk' reflectorm may be readily turned out of position when not in use and when the instrument is to be used for subjective tests, the said retinoscopic mirror and reflector are mounted, as shown in Fig. 1 and in the detail sectionFig. 4, upon a supporting-bar '19,-

of square form, which rests beneath the end of the beam D and is pressed against the said beam by a bearing-spring r to hold it in position. For this purpose the harp is formed near its forward end with a cylindrical journal q, Fig. 4, by which it rests inthe yielding bearingr, so that the connected retinoscopic mirror f and the reflector m may be sure of the corner of the square harp against the bottom of the'beam D and then pressing,

the side or top of the square .barp, as the case may be, against the bottom of the beam,

' D, so as to hold said reti'noscopic mirror and forwardend of the slidable bar D, so as to in dicate accurately the position of, the lens-cell b in subjective tests, and near the rear end of the beam is a scale s, which may be read from the rear end of the slidable bar (1 in objective or retinoscopic examinations.

From the above description it will. be understood that instead of moving the retinoscopic mirror by hand, which is the method heretofore employed, I obtain the same phenomena of the transit of the retinal reflex and penumbra by shifting the light itself, which is fastened to the end of the rod g, which is inclined at an oblique angle, starting from a point a few inches removed from the retinoscopic mirror, extending upward and backward to a point twelve inches, more or less, over the patients-head, and twelve.

or more inches backward of the same, where the electric lamp h is mounted on said rod.

'grees.

D, near its front qua non is impossible.

The protractor-scale j on the periphery of the circular cell j is preferably marked to indicate t'he different meridional angles, ranging from zero to one hundred and eighty de- The entrance of the handle or rod g through the slot is in the disk k, which is rofalteringly in each individual meridian by 'rotating'the disk It to any particular meridian and then sliding the rod along the axis of the slot.

Operation: In objective or retinoscopic examinations the operator directs the patient to place his eye to the concave ocular at a, while he seats'himselt' in juxtaposition, placing his eye 'to the stationary retinoscopic mirror or looks through the same from the pointo through the medium of the perforated disk n and reflector m. With one hand he moves the rod, which projects through the governor or slot in the disk, and sweeps the light in anydirection that may be needed, while with his other hand he grasps the milled head 0 of the pinion-shaft and rotates thesame, therebyincreasing or decreasing the refractive power of the lens combination u ntil the choking of the retinal reflex is obtained. The amount of lense-power is indicated on the scale directly in front of the mirror, thus not necessitating his getting up to observe the results of his labors.

All instruments-that have hitherto been designed for this method of eye-measuring require the retinoscopic mirror to be held either loosely in the hand or-;held within a gimble to be manipulated by the hand. The light that is deflected by this mirror is exaggerated in its rapidity in ratioto the. distance between the .mirror and the observed eye, the greater the intervening distance the greater the rapidity of the transit of the light. This being so in ninety-five cases out of a hundred, the operators process of mental differentiation cannot keep pace with the phenomena that he observes on his own retina while trying to compute the error in the observed eye, the result being mental dubiety. Furthermore, in all previous instruments the skiascopic mirror must be held close and tilted directly against the eye of the operal tor, said tilting being the result of what is known as wrist motion. This objection I surmount by having the mirror stationary,

but generating the movement of the electric light and its sequence (the fundusreflex) by controlling the same by the handle of the rod 9 as .it emerges through the slot in the disk It and at a point sufiiciently far away .to insure the necessary steadiness.

In measuring each meridian of the eye it is necessary that the. transit of -the light should describe a straight unswerving line across the pupil. With previous instruments the sine With my instrument,

by virtue of the. slot in the disk It, I. have a governor which absolutely precludes a swerving of the light in any direction other than that which the operator desires.

A perfect instrument should be so constructed that each of its cardinal points of mechanism canbe simultaneously under the control of the operator. This desideratum is realized in my invention.

15 represents a mirror mounted on the frame of the apparatus, by which the patient is enabled to fix his eye upon a distant object in the rear in order that the pupil of the eye may be in normal condition during the examination.

Having thus described my invention, the following is what I claim as new therein and desire to secure by Letters Patent:

1. In an instrument for the examination of the eyes, asuitable support, stationary means containing the observation-aperture for directing the rays of light to the eye'under examination combined with movable light-supply means for cooperation with said light-directing means, as set forth.

2. In an optometrical instrument, the combination of a horizontal supporting bar or frame,a stationary retinoscopic mirror mounted on one end of said bar, an eyepiece mounted on the other end of said bar, and a lensholder mounted on a separate sliding bar, and adjustable in relative distance between the retinoscopic mirror and eyepiece,as described.

3. In an optometrical instrument, the combination of a retinoscopic mirror, a support on which it is mounted and held in fixed position, a suitable lens-holder for retinoscopic examinations, and a lamp mounted on an adjustable support and movable in angle relatively to the retinoscopic mirror,substantially as and for the purposes set forth.

4. In an optometrical instrument, the combination of the support D, eyepiece a, mounted at one end thereof, lens-holder I) mounted on a sliding support D and adjustable relatively to the eyepiece; the hinged support 13 and retinoscopic mirror f mounted thereon, adapted to be fixed in stationary position for use, and to be removed from the line of vision,

when the instrument is to be used for other than retinoscopic examinations,as explained. 5. The combination of a suitable support D, an adjustable lens-holder b, a retinoscopic mirror f mounted on the support in fixed position for use, and a reflector m mounted on a support in rear of the retinoscopic mirror, substantially as described.

6. The combination of the beam D adjustable lens-holder Z7, retinoscopic mirror f, reflector m and perforated disk or finder, substantially as and for the purposes set forth.

7. The combination of the beam D adjustable lens-holder Z), support 19 movably mounted on the beam D, the retinoscopic mirror f mounted on the movable support 19, and the reflector m mounted on said support in rear of the retinoscopic mirror and in line with the axis thereof, whereby the said-retinoscopic mirror and reflector are held in fixed position while in use and are adapted tobe moved out of the line of vision when not in use, as explained.

8. The combination of the beam D, adjustable lens-holderb, the sliding bar D on which the lens-holder b is mounted, a mechanical adjusting device 0 for sliding the bar D, a retinoscopic mirror f mounted on the rear end of the beam D in fixed position for use, and a lamp 71. mounted upon an adjustable support 9, to permit the angular movement of the lamp relatively to the retinoscopic mirror, as explained.

9. The combination of the beam D slidable bar D, lens-holder I) mounted on said bar,

retinoscopic mirror f mounted on the beam D in fixed position for use, movable lamp h, rod g, on which said lampis mounted, slotted disk It, in which the rod 9 is guided, and the annular holder j, in which the slotted disk I.) is mounted rotatably, to permit the placing of the slot therein at any angle, to determine the plane of movement of the lamp h, as explained.

10. The combination of the support D, eye piece a, adjustable lens-holder b, retinoscopic mirrorfia'nd the mirror t mounted on the support in position, to enable the patient to view a distant object reflected in said mirror,while the eye is under retinoscopic examination, as explained.

L. L. FERGUSON. 

